Submitted to: American College of Veterinary Pathologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/22/2006
Publication Date: 7/22/2006
Citation: Okubara, P.A. 2006. . .
Technical Abstract: Necrotrophic root pathogens cause chronic yield losses in cereal-growing regions of the Pacific Northwest and throughout the world. We have developed real-time PCR assays for pathogenic Pythium and Rhizoctonia spp. isolated from symptomatic sites throughout the dryland cereal production regions of the Pacific Northwest. In collaboration with Dr. Tim Paulitz, USDA ARS, Pullman, WA, we have used these assays to determine that P. ultimum, P. irregulare and P. irregulare group IV are the most pathogenic to wheat and barley, whereas P. abappressorium and P. rostratifingens are the most prevalent in Pacific Northwest soils. Likewise, R. solani AG-2-1, R. oryzae group III and binucleate AG-I-like Ceratobasidium spp. are prevalent. Biological control offers a sustainable approach to the control of soilborne necrotrophic pathogens. Biocontrol strains of Pseudomonas fluorescens suppress root diseases by the production of antifungal metabolites and by other mechanisms, display preferences for host species, and differ in ability to persist in the rhizosphere. Although much less is known about host-dependent factors that govern species preferences and rhizosphere persistence, we hypothesize that host genes contribute to the effectiveness of biocontrol P. fluorescens, and that these genes can be recruited for stronger and more durable control of root diseases. We have determined that cultivars of the host Triticum aestivum (hexaploid wheat) vary in ability to sustain root populations of biocontrol strains and to accumulate the antifungal metabolite 2,4-diacetylphloroglucinol (2,4-DAPG) on the roots. Microarray analyses of wheat root mRNAs (cDNAs) indicated that genes involved in jasmonic acid signaling, oxidative stress and programmed cell death are induced in during colonization with biocontrol P. fluorescens. The changes in gene expression were authenticated using real-time PCR.